Continuous-casting mold



Sept. 15,1970

E. T- VOGEL vCONTINUOUS"CASTING MOLD Filed May 20, 1968 INVENTOR I ERIC T. VOGEL mimum United States Patent U.S. Cl. 164273 4 Claims ABSTRACT OF THE DISCLOSURE A mold assembly for a continuous-casting mold, which has an open-ended mold cavity therethrough, is in two parts which separate at a plane extending axially through the cavity. The parts are moved together and apart by suitable power means, such as pistons in cylinders operated by fluid pressure. In the closed position of the mold one of the parts is positioned at the plane of separation by pressing it against stops and the other part is pressed against the first part. Greater pressure is applied to press the first part against the stops than is applied to press the other part against the first part, so that the plane of separation is at a fixed position determined by the stops, and suflicient relative pressures are applied to hold the parts firmly together at the plane of separation. At the end of a casting run both parts are adapted to be moved back from the plane of separation to assure complete release of the casting.

The present invention relates to a mold assembly for the continuous casting of metal, such as steel. In particular the invention is a mold assembly in which the mold is separable in two parts for releasing the tail end of a cast strand and which incorporates simple and effective means for holding the mold parts firmly together during casting.

In continuous casting, molten metal is poured into one end of an open-ended mold cavity which is through the mold. The mold is cooled and solidifies the periphery of the metal in the cavity to form a cast strand which is drawn out of the other end. Additional metal is poured into the cavity to replace the metal drawn out as a continuously cast strand. At the end of a casting run, the flow of molten metal into the mold is stopped and the tail end of the cast strand is left in the mold long enough for its upper end and sides to solidify. This is referred to in the art as capping the strand. When the tail end is solidified, or at least sufficiently solidified to contain any metal which may still be molten in the core of strand, it is withdrawn from the mold. Of course, the tail end of the strand shrinks as it solidifies, and if it is round, rectangular, or some other cross-sectional shape which is not indented or deeply concave, the shrinkage loosens it in the cavity so that it is easily drawn out. If, however, the cross-sectional shape of the strand is deeply indentedas in the cases of channel, rail, I, or dog bone (bulbous ends with a slim section between) shapes, for examplethe inner walls of the indentation or indentations shrink against the corresponding wall surfaces of the mold cavity and lock the tail end of the casting in the mold so that it is difficult or impossible to withdraw. This problem is customarily avoided by limiting the depth, steepness and sharpness of the indentations of cross-sectional shapes that are cast with continuous-casting apparatus, and by tapering the molds. The molds,

3,528,485 Patented Sept. 15,, 1970 however, can only be tapered to a small extent without rendering them inoperable. Consequently, when it is desired to use continuous-casting methods to produce channels, rails, I beams or other shapes having deep and/or sharply defined indentations, the initial cast shape must be modified to reduce the depths and sharpness of the indentations so that the casting must subsequently be forged or rolled to a considerable extent to produce the desired shape. This increases the cost and reduces the advantagesnamely, increased production rates, reduced cost of equipment and greater economy of operationof continuous casting as compared with alternate forming methods consisting of casting ingots that are first hammered and rolled into blooms and billets and subsequently rolled or forged into the final shapes desired.

It is therefore an object of the present invention to provide a continuous-casting mold assembly wherein the mold is separable in two parts from around the tail end of the casting whereby the mold cavity may be formed for casting strands having cross-sectional shapes with relatively deep, sharply-defined indentations without the tail end of the casting sticking in the mold when it has been capped at the end of a casting run. This makes it possible to cast strands which have more nearly the final indented shape desired than is possible with conventional continuous-casting mold assemblies. Consequently, the number of forging or rolling operations to give the casting the desired final shape, and hence the cost of producing the finished article, is greatly reduced.

Another object is to provide a mold assembly wherein the mold is separable in two parts, and which includes simple, rugged means for moving both the parts together and apart with respect to a precisely located plane of separation and for holding the parts firmly together during the casting.

Molds separable in parts for releasing a casting are known in the casting art in general, but up to the present there has not been a practical separable mold for use in continuous-casting. It is believed this is due to the particular problems involved in providing an etfective and economic separable mold for continuous-casting. For example, a mold which is separable in two parts must be adapted for the parts to be held firmly together in a manner to withstand separation by the considerable ferrostatic pressure of metal in the mold cavity, and yet be readily separable to release the casting. Moreover, in order to ensure complete release, both separable parts of the mold should be drawn back away from the casting while the casting is held stationary in one axial position. Otherwise, if only one part moves, the casting might stick to the other. In accordance with the present invention, the mold assembly includes a mold in tWo parts which are separable at a plane extending axially through the mold cavity. The parts are held together under pressure applied by suitable means, such as pistons movable in fixed cylinders by fluid pressure. In the closed position of the mold one of the parts is pressed against stops, which locate the position of the plane of separation of the parts, and the other part is pressed against the one part by a pressure which is less than the pressure applied to press the one part against the stops. The lesser pressure is made great enough to hold the other part against the one part with sutficient pressure to resist being forced away from the one part by ferrostatic pressure during casting.

The pressure to hold the parts together could be applied by any suitable means, such as cylinders with pistons, as mentioned above, springs, or a combination of these.

The mold parts could also be moved apart by toggle mechanism of the type illustrated in copending application Ser. No. 728,217 filed May 10, 1968, assigned to the same assignee as the instant application, wherein the parts are held together under pressure and are separated by toggle mechanism which is operative to apply sufficient counter pressure to overcome the pressure holding the parts together.

In the illustrative embodiment described in detail below, the mold parts are moved together and apart by the pressure applying means which is provided by pistons movable in fixed cylinders by fluid pressure. Piston rods from the pistons are attached to the respective mold parts and fluid, such as air, oil or water is applied to the cylinders in a conventional manner for selectively pressing the mold parts together and moving them apart.

The mold assembly of this invention therefore provides an effective two-part separable continuous-casting mold adapted for casting strands having deeper and sharper identations in their cross-sectional configurations which cannot be cast with one-piece molds.

A particular feature of this assembly is that, when the mold parts are separated for releasing the capped tail ends of a cast strand, both mold parts move back from the plane of separation of the parts and thereby assure complete release of the cast strand.

In addition the means for holding the mold parts together are such that the plane of separation of the parts, and hence the position of the mold cavity, may be precisely positioned relative to the support and guide means which conduct the cast strand emerging from the mold away from the mold. Thus, the mold cavity can be placed in the best alignment for delivering the cast strand to the support and guide means without marking, or unnecessarily bending the strand. The hold means of this assembly also assures that the alignment will be maintained during casting, and for successive casting runs.

An illustrative embodiment of a mold assembly in accordance with the invention is described below with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of a vertical section through a continuous-casting mold, and through a guide apron extending from below the mold, to illustrate the general structure and arrangement of a mold assembly in accordance with this invention;

FIG. 2 is a view of a horizontal section through the mold, and through pressure applying devices, of a mold assembly embodying the invention.

Referring to the drawings, FIG. 1 illustrates schematically a continuous-casting mold assembly of this invention in use.

In a continuous casting molten metal, such as steel, is

poured from a supply indicated by the outlet of a tundish, into the upper end of an open-ended mold cavity 11 of a mold 12. The walls of the mold cavity 11 are cooled by suitab e means, such as by circulating water through channels in the mold or through a jacket around the mold, to solidify the periphery of the metal in the mold to form a strand 13 which is drawn from the bottom end of the mold cavity.

At the start of casting, the lower end of the mold cavity is stoppered with a plug (not shown) which is customarily provided with a mushroom shaped projection or undercut portion around which the metal in the mold solidifies to fuze the plug to the lead end of the strand 13 being formed in the mold. When sufiicient molten metal is backed up in the mold by the plug for a strand to form, the plug is withdrawn to start the strand down, out of the lower end of the mold cavity. Guide rolls 14 mounted to be at opposite sides of the emerging strand 13 assist the withdrawal of the strand from the mold cavity and guide the strand into a support and guide apron 15, which conducts the strand away from the mold. In the drawing the apron 15 is indicated as being a curved chute; in practice the apron 15 may be provided by a sequence of support rollers, support panels or other suitable means. The strand 13 may be conducted straight down from the mold, but in many conventional continuous-casting machines the strand is conducted along a curved path, as shown, to lead it into a horizontal path which is more convenient for subsequent forming or cutting operations.

When the strand emerges from the mold, its core is still molten and further cooling is applied, first to prevent the molten core from rernelting the solidified periphery or skin of the strand and then to further solidify the strand. For this purpose cooling means, such as water sprays, indicated at 16, are applied to the strand at spaced intervals therealong.

The casting operation is continued by pouring molten metal into the top of the mold cavity to replace metal comprising the strand emerging from the bottom of the mold cavity. To end a casting run the flow of molten metal to the mold is discontinued and the strand is capped by halting the withdrawal of the strand until the tail end of the strand in the mold solidifies completely. If the crosssectional shape of the strand formed by the shape of the mold cavity is round, rectangular or some other shape which does not have indented portions, the shrinkage of the solidifying metal loosens the strand in the mold; but if the shape has deep indentations or undercut portions as with the cross-sectional shapes of rails, I beams and channels, for examplethe shrinkage of the metal locks the strand into the mold cavity. This locking-in of a capped strand is avoided in a mold assembly in accordance with the present invention wherein the mold 12 is in two halves 12a and 12b which separate along a vertical plane axially through the mold cavity 11.

During casting, the mold halves 12a and 1212 are held together by pressure applied to the outward-facing sides of the mold halves by pressure means, such as the pistons 17 in cylinders 18 having piston rods 19 attached to the mold halves. Other pressure means, such as springs, or a combination of springs and pistons 17 could be used, but the pistons are particularly suitable since they are adapted to provide simple effective means for separating the parts 12a and 11212 for opening the mold, as well as for pressing the parts together to close the mold. As shown in FIG. 1, hoses 20 and 21 are connected to ports respectively through opposite end portions of the walls of cylinders 18 to open respectively at opposite sides of the pistons 17, and fluid, such as air, oil or water is applied through the hoses 20 and 21 for pressing the pistons 17 to one or the other ends of the cylinders 18, depending on whether the mold parts 12a, 12b are to be pressed together or moved apart. This is readily accomplished with conventional connections and valves (not shown) which are operable to direct fluid under pressure from a suitable source (not shown) alternatively into one of the hoses 20, 21 while 1ripening to relieve the pressure from the other of the oses.

Referring to FIG. 2, the cylinders 18, 18' for the respective mold halves 12a, 1212 are mounted in fixed positions through a frame 22 which extends around the mold 12. Sufficient clearance is provided between the mold 12 and the frame 22 for the mold halves 12a, 12b to move, as necessary to separate and come together, within the central opening of the frame 22. Piston rods 19, 19' from the pistons 17, 17 in cylinders 18, 18' extend inward from opposite sides of the frame and their inward ends are attached to the sides of the respective mold halves 12a, 12b. Matching guides (not shown) of conventional construction and arrangement will ordinarily be provided in the end walls of the mold halves 12a, 12b, and in the end walls of the frame 22 which are adjacent to the end walls of the mold halves, to guide and support the mold halves for their movement toward and back from each other by the operation of the pistons 17, 17.

The mold halves 12a, 12b separate along a plane which is axially through the mold cavity 11. The lateral position of the plane is selected in accordance with the crosssectional configuration of the mold cavity 11 and is located so that the arrangement of undercut portions of the configurationor sharply indented portions-relative to the plane of separation is such that these portions will not lock a casting in the mold and prevent or impede the movement of one or the other of the mold halves back from the plane. For symmetrical configurations the plane of separation may suitably be made to coincide with the plane of symmetry of the configuration, as illustrated by the mold halves 12a, 12b shown in FIG. 2.

When the mold 12 is in closed position a face surface 23 of mold part 12a and a face surface 24 of mold part 12b are in abutting relation and define the plane of separation. When the mold parts 12a and 12b are moved toward each other, by pressure applied by the pistons 17, 17', to close the mold, the mold part 12a moves in toward, and engages, stops 25 which hold the mold part 12a in a predetermined inward position. For this purpose, the ends of the mold part 12a are provided with outwardly projecting shoulders 26 that are in line to engage the stops 25 which project inwardly from opposite ends of the frame 22. As the other mold part, 12b, moves in, its face surface 24 moves into abutting relation with the face surface 23 of mold part 12a, and greater pressure is applied to hold the mold part 12a against the stops 25 than is applied to hold mold part 12b against mold part 12a. Thus, the two parts are firmly pressed together at a plane of separation, the position of which is located by the position of the stops 25.

As shown in FIG. 2, the different pressures applied re spectively to the two mold parts 12a, i121; for holding them together is provided by having the cylinders 18' and pistons 17', which are operatively connected to mold part 121), a smaller diameter than the cylinders 18 and pistons 17 for the mold part 12a so that the pistons 17' apply less mechanical force than pistons 17. In thiscase the pistons 17, 17' may be operated by connecting their cylinders 18 and 18' to a single source of fluid under pressure. Alternatively, the difference in mechanical force applied to the mold parts 12a and 12b could be provided by connecting each of the sets of cylinders 18 and 18 to a different source of fluid with the fluid being at a different pressure at each source. In this latter instance the cylinders 18, 18' and pistons 17, 17 could either be all the same diameter, or different diameters, respectively, as illustrated in FIG. 2. In any event, lesser pressure applied to hold the mold part 12b against the mold part 12a is made sufficiently large so that the pressures applied to the respective mold parts 12a and 12b will hold the mold parts together firmly enough to resist separation by the ferrostatic pressure of metal in the mold cavity 11.

As mentioned above, the location of the plane of separation of the mold parts 12a, 12b is determined by the position of the stops 25, which are on the frame 22. Thus, the plane of separation of the mold parts, and hence the position of the mold cavity 11, are in fixed relation to the frame 22, so that the exit end of the mold cavity 11 may be accurately aligned with the upper end of the guide apron 15for smooth passage of a cast strand from the mold cavity onto the guide apronand will not be shifted out of alignment by thermal expansion of the mold parts or by repeated openings and closings of the mold.

The frame 22 has lugs 27 projecting from opposite ends with holes 28 through the lugs for supporting the frame 22, and mold 12 therein, on a conventional mold table (not shown) of conventional continuous-casting apparatus. The mold table has a central opening, and the mold 12 in frame 22 is supported therein by the lugs 27 which rest on portions of the mold table at opposite sides of the opening. Pins projecting up from the mold table are received through the holes 28 in the lugs 27 for positioning and holding the frame 22 on the mold table.

The mold 12 is customarily cooled by water, or other fluid coolant, circulating through passages in the mold walls or through a jacket around the mold. Suitable structure for cooling the mold parts 12a and 12b is disclosed in copending US. patent application Ser. No. 728,217, filed May 10, 1968.

The mold cavity 11 of the embodiment illustrated in the drawings is a straight cavity. It will be appreciated, however, that the mold assembly of this invention is equally adapted for an assembly in which the mold has a curved mold cavitycurving in an arc from one open end to the other. If the mold cavity is curved, the interface between the separable parts may be true flat plane through the cavity as in the embodiment described above. Or the interface may be curved-to follow the curvature of the cavity, for example. In the latter instance, the curved interface would not define a true plane since technically the term plane refers to a flat surface. In the present context, however, the mode of operation and the essential structure of an assembly, in accordance with this invention, are the same whether the interface between the separable mold parts is a flat or a curved surface. It is therefore intended that the expression plane of separation, as used herein, refers to the interfacial surface defined by the mold parts when they are together whether the interfacial surface is flat or curved.

It is to be understood that the embodiment of the invention shown in the drawings and described in detail above is illustrative only and that the structure and mode of operation may be varied without departing from the scope of the invention defined by the following claims.

What is claimed is:

1. A mold assembly for a continous-casting mold having an open-ended cavity therethrough wherein molten metal poured in one end of the cavity is peripherally solidified in the mold and withdrawn as a cast strand from the other end, said assembly comprising a mold separable in two parts at a plane extending axially through the cavity, each mold part having a face surface adapted to abut the face surface of the other mold part at the plane, and each mold part being movable toward and away from the plane, one mold part having a stop engaging surface, first pressure means operative on one mold part and second presure means operative on the other mold part for urging the respective parts toward the plane, and stop means to be engaged by said one mold part for stopping the movement of the one mold part toward the plane at a position in which the face of the one mold part is at the plane, said first pressure means being adapted to apply greater pressure to said one mold part than the second pressure means applies to the other mold part for causing the face surfaces of the parts to be held in abutting relation at the plane with the first pressure means pressing the one mold part against the stop means, and by the second pressure means pressing the other mold part against the one mold part with pressure less than the pressure of the one mold part against the stop means.

-2. The assembly of claim 1 in which said pressure means are adapted to apply releasable pressure, and which includes means for moving the mold parts back away from said plane.

3. The assembly of claim 1 in which said pressure means comprise pistons movable in fixed cylinders by fluid pressure, said pistons having piston rods connected respectively to the mold parts, and connections adapted for supplying fluid under pressure to each of the cylinders to move the pistons therein in directions respectively for moving the parts toward said plane, and then in opposite directions for moving the mold parts back away from said plane.

4. The mold assembly of claim 1 which includes in combination guide and support means mounted in fixed position relative to said plane adjacent the end of the mold cavity from which a cast strand emerges for supporting said strand in fixed axial relation to said plane, and

means for moving each of the mold parts back away from said plane.

References Cited UNITED 3,528,485 8 FOREIGN PATENTS 533,303 11/1956 Canada.

STATES PATENTS J. SPENCER OVERHOLSER, Primary Examiner Betterton et a1. 164-82 5 R. SPENCER ANNEAR, Assistant Examiner Ratcliffe 164280 Buckwalter et a1 164-283 US. Cl. X.R.

Pearson 16482 X 343 

